Various example embodiments relate to a semiconductor memory device, and more particularly, to a semiconductor memory device controlling a refresh cycle, a memory system, and a method of operating the semiconductor memory device.
Capacities and speeds continue to increase for semiconductor devices, widely used in high performance electronic systems. A dynamic random access memory (DRAM), i.e., an example of a semiconductor device, is a volatile memory, wherein data is represented by charge stored in a capacitor. Since the charge stored in the capacitor leaks over time, DRAM memory cells have a finite data retention characteristics.
A refresh operation is periodically performed to maintain data stored in the memory cell of the DRAM. Timing of the refresh cycle is often determined based on design specifications, wherein a refresh cycle having a uniform value is applied to all memory cells. However, since the level of difficulty of the process technology is increased according to a continuous DRAM process scaling, uniformity of processing across the DRAM device deteriorates which may cause manufacturing production yield to deteriorate.